Melatonin Secretion Related to Side-effects of β-Blockers from the Central Nervous System

ABSTRACT In two studies of hypertensive patients the relationship between β-blocker-induced CNS side-effects and the nightly urinary secretion of melatoninwas analysed. In one group (n=10) placebo, atenolol(mean dose 86 mg/day) or propranolol (mean dose 305 mg/day) were given in a double-blind, randomised design. In the other (n = 13) 100–400 mg metoprololwas given daily (mean dose 197 mg). After 4 weeks of treatment all β-blockers reduced melatoninexcretion, but the effect was significant only for metoprolol. Sleep disturbance records revealed more disturbed nights in the metoprololgroup compared with the propranolol and the atenololgroups, even when the difference in age between the groups was controlled for. In the metoprololgroup a significant relationship (p<0.05) was found between the fall in melatoninand the percentage of disturbed nights. Severe CNS side-effects, such as nightmares, occurred only in patients treated with metoprolol(21%), which in all cases were accompanied by low levels of melatonin. Our data suggest that the CNS side-effects during β-blockade are related to a reduction of melatoninlevels.